Zero detector for electronic counters



Dec. 16, T952 R. E. SPRAGUE ETAL ZERO DETECTOR FOR ELECTRONIC COUNTERS Filed Dec. 20, 1948 AM@ 4M@ ,4X 14)/ .C L www W me@ N PK 2 m56 o W@ M 106. l 4 CN ww ln Y B L I x n k Ha 0. 0,. 5 T 7 TT a@ A, A, 4u .um @.0 6m. WW MN um om c 0M am a .wd Cm y Vp WM Patented Dec. 16, 1952 ZERQDETECTDR' FOBn ELEQTIRQNIC.

' vooUrrrEas BichardfELSpAlagup, Redondo Beach, and, Donaldk Ef. Bird-ahi.; Nprthrop, Ai

Hawthorne Calif. @astenersi t0.- raft, Inc., Hawthorne, Calif., a

amargura.ctalifenia' o Applcationlleoember 20, 1MB-Serial No. 66,254

8, Claims. 1; Our invention relates tg. zere deiegtgrsfeier electronic counters., and; me te zere detectors ierernultistaee s Aceu-Hi which will provide an entre vwheeerer the Counters are cleared er. passim-Quell. number content condition.l

In electroni@ counting equipment. it: ad.- Venteeeeue te knew, When-the number geniet of a multistage counter` becomeszero, oer tain instances, Whenthecou ter` goes, through zero, the manner-in whiehca pulsesbetween Stages is medey must berevetsea@ The-grenat invention oiers a solutionT to vthis plfcblerrrv in tects the Zero.numbercontent-fcon tionl of -th'e counter, and provides this information inthe form of a static voltage .output, a dynamic pulse output or a visual, indicationfdepending. upon the location in thecircuit the oui',put s taken.

The present invention is applicable.y toy any multistage counterwherein an indicating element such as a neon glow tube, forexample; c anbe used to indicate a zero condtionzat each digit stage of the counter. In broadfterms, when none of the indicating elements are. energized, v indi-i eating a Zero number contentcQnd-tionof the counter, a vacuum tube is caused tocoductf. This conduction isethenusedtocreatea sube, stantial change` in output` voltage, to. createfa pulse or to give avisualv indication;

It is an object of thefrpresent invention to. vprovide a means andmethod of indicatingsthejz'em number content condition of an electronic counter and to ,provider such an indication as a change of Voltage or a pulse.

Other objects andadvantagesofj our invention will be more apparentk from t @ensuing description ofthe drawingainwhi Figure 1 is e Circuit dieeramioi, one, meier-red. form of our invention,

Figure 2 is a graph seduencefofr voltage condie tions at various points in thecircuitof Figurevl.

Figure is a circuit diagramfooneg-type .of control circuit operated by the-.circuit ot Figurel.

Figure 4 is a circuit diagram of one type of visual indicator operatedfb-yf thecirc-uit rof Figure 1.

In Figure 1,. C represents e, multistage counter f env type er System, Where, a, current `earn'ine indicator such as a neon glowlampli attached to. one point in` eachcourrter staget S, ofA the counter C so that the lampishqi'vwhen the counter stage contain/st the-digitaero and-is .on

when theeeunter staeeeentain., anyzvther digit l 2.k Normally, neon lamps of this nature are valready used in counters.

To this end, each lamp L is connectedthrough an individual resistance l`t1Y to avoltage. source B of high positive voltage through av common resistor R2. The grid and cathode of avacuum tube T1 are connected across resistor Rg. The anode of tube T1 is Aconnected-1thrOi-leh anode resistor Rs to a second voltagesource, D which is preferably maintained ata higher voltagethan thatof source B,

The output of tube T1 is taken from between the anode of tube T1 and ,anode resistorR3 and is led to the grid of a second tube T2 through a differentiation circuit comprising4 a seriesvcapacitor-.C1 and a shunt resistance R4. The anode of tube T2 is directly connected to` a VQliiage source E andthe cathode oftube. T2 is connected to ground through an inductance L1. A diode Ts is connected across inductance L1, with the anode thereof continuedas a.r pulse. output PO.

In operation, graph l of Figure 2 shows the number content ofthe counter C as successive pulses are applied at its input in a subtractive fashion. As these subtractive input pulses are fed into the counter previous to. zero content, some of the lamps L are lit anda currentflows through resistor R2 through resistor R1 and through each lit lamp to the connected counting stage S. The voltage drop. across resistor R2 due to the current flowing through it, keeps the voltage of the grid of tube T1 suiciently negative that'tube T1 does not conduct. Under this condition the voltage at point. A can .be made to be the same as at point D, as indicated in graph .2 .of Figure 2. This condition exists irrespective of the. number of lamps lit.

However, if no lamps are lit, as when zeroA number content is in the counter,l n o current ows through resistance R2 and the gridA of tube, T1 is energized to be of the proper voltage so, that: tube T1 conducts., The change otfvoltagefat point A ofthelcircuitof Iiigvu-reol,y as shown in graph 2 of Figure 2, is then diiterentiated in the circuit com binationof condenser Crand resistor'Ri with a voltage curve, as `shown in .graph 3 .of `Figure 2. Thisvoltage-energizes tube T2 and a pulse output PO, as shown in .graph 4 of Figure 2,( results due @the eenen of therme-ieeeireuitlt Te and L1- either a velate-ee etrangers, pred-need, (et point, A) 0r. apulse ismede ,available at, pulse'outeut-:PQ One 0r 'both Oefthese. output vcan be usefies Signat. or-fortheenereization of edditiena eireuits that een shift conditions, in counter 3 C when the zero condition is passed through or reached, or both.

It is to be noted that in the circuit or Figure lJ the neon glow lamps L serve automatically to isolate each stage, while in the zero condition, from potential changes due to operation of other stages.

By way of example, assume that one of the neon lamps L is non-conducting, i. e., the stage S to which it is connected is in the zero condition. Now, assume that, as the counting proceeds, one of the other neon lamps L changes from a nonconducting to a conducting condition, due to the fact that the stage S to which it is connected changes to a number or conducting condition. At this instant a negative pulse is created on the common lead connecting all the neon lamps to the indicator` tube. This negative pulse might be communicated to the non-conducting neon bulb connected stage and thus undesirably change the condition of that stage, were it not for the fact that the non-conducting neon bulb has a very high impedance, and the negative pulse created on the common lead is not of sufcient magnitude to nre a neon lamp.

In Figure 3, the output PO from the ringing circuit is led to a flip-nop circuit FF of any wellknown type, the output of this circuit FF being connected to energize a pair of amplifiers Ax or Ay in accordance with the condition of the ilipflop circuit. The respective outputs :c and y can then be used to change conditions in counter C as desired. One exemplary condition may be to stop the counting at zero.

In Figure 4, the flip-nop stage FF energized by pulse output PO is used to energize a zero indicating lamp LI, this lamp being lit, for example, as the counter passes through the zero condition from a positive number to a negative number, and being unlit as the counter passes through zero from negative to positive number content.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modication in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specic as to structural features, it is to be understood that the invention is not limited to the specic features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect, and the invention is, therefore, claimed in any of its forms or modications within the legitimate and valid scope of the appended claims.

What is claimed is:

1. In combination with a counting device having one or more stages having a portion passing substantial current for a number condition of each stage and passing negligible current for the zero condition of each stage, each of said portions including a visual indicator glow lamp of the diode type connected to be off for the zero condition only, zero indicator means for said device wherein the circuit for supplying current for said glow lamps comprises a common d. c.potential source forming the positive side of said circuit, and including resistance means common to all of said glow lamps and connected to said-potential source between said lamps and said source, a three electrode vacuum tube held in non-conducting condition by the voltage drop across said common resistance, the constants of said tube being arranged so that said tube is conducting when no substantial voltage drop loccurs across said common resistance, a differentiation circuit fed by said vacuum tube, and a ringing circuit having a pulse output fed by said differentiation circuit.

2. Apparatus in accordance with claim 1 wherein a nip-flop stage is connected to be operated by said pulse output.

3. Apparatus in accordance with claim 1 wherein a nip-flop stage is connected to be operated by said pulse output, and wherein a visual indicator is connected to be operated by the condition of said flip-nop stage.

4. Apparatus in accordance with claim 1 wherein a flip-flop stage is comiected to be operated by said pulse output, and wherein a pair of amplifiers are connected to be energized in accordance with the condition of said flip-flop stage.

5. In combination with a counting device having one or more stages having a portion passing substantial current for a number condition of each stage and passing negligible current for the zero condition of each stage, each of said portions including a visual indicator glow lamp of the diode type connected to be off for the zero condition only, zero indicator means for said device wherein the circuit for supplying current for said glow lamps comprises a common d. c. potential source forming the positive side of said circuit, and including resistance means common to all of said glow lamps and connected to said potential source `between said lamps and said source, a three electrode vacuum tube held in non-conducting condition by the voltage drop across said common resistance, the constants of said tube being arranged so that said tube is conducting when no voltage drop occurs across said common resistance, a differentiation circuit fed by said vacuum tube, a ringing circuit having a pulse output fed by said diierentiation circuit, and indicating means operated by said pulse output.

6. In combination with a counting device having one or more stages having a portion passing substantial current for a number condition of each stage and passing negligible current for the zero condition of each stage, each of said portions including a visual indicator glow lamp of the diode type connected to be off for the zero condition only, zero indicator means for said device wherein the circuit for supplying current for said glow lamps comprises a common d. c. potential source forming the positive side of said circuit, and including resistance means common to all of said glow lamps and connected to said potential source between said lamps and said source, a three electrode vacuum tube having the grid and cathode thereof connected across said resistance, a second source of voltage higher than that of said first source connected to the anode of said Vacuum tube, said tube being biased to conduct in the absence of a voltage drop across said resistance and to be non-conductive when a resistance drop is present across said resistance, and an output circuit connected to said anode.

7. In combination with a counting device having one or more stages having a portion passing substantial current for a number condition of each stage and passing negligible current for the zero condition of each stage, each of said portions including a visual indicator glow lamp of the diode type connected to be off for the zero condition only, zero indicator means for said device wherein the circuit for supplying current for said glow lamps comprises a common d. c. potential source forming the positive side of 4said circuit, and including resistance means common to all of said glow lamps and connected to said potential source between said lamps and said source, a three electrode Vacuum tube having the grid and cathode thereof connected across said resistance. a second source of Voltage higher than that of said rst source connected to the anode of said vacuum tube, said tube being biased to conduct in the absence of a voltage drop across said resistance and to be non-conductive when a resistance drop is present across said resistance, an output resistance between said anode and said second source and an output connection to said anode.

8. In a counting device having a plurality of stages each having a portion passing substantial current for a number condition of its stage and passing negligible current for the zero condition of that stage; zero indicator means for said device comprising a series combination of a visual indicator glow lamp of the diode type and an external resistance for each of said stages, one end of each said combination connected in its corresponding CIN stage portion, a common d. c. potential source, a common resistance connected between said potential source and the other ends of each of said combinations, said potential source and said resistanoes being proportioned so that each of said glow lamps is on for said number condition of its associated stage and off for said zero condition; and a three-electrode vacuum tube, said common resistance being connected between the grid and cathode of said tube, the constants of said tube being arranged so that said tube is conducting when no voltage drop occurs across said common resistance, and nonconducting when a voltage drop across said common resistance occurs as a result of one or more glow tubes being on.

RICHARD E. SPRAGUE. DONALD E. ECKDAHL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,402,988 Dickinson July 2, 1946 2,422,698 Miller June 24, 1947 2,500,294 Phelps Mar. 14, 1950 

